As this type of radius end mill, for example, Patent Citation 1 suggests a radius end mill in which a main gash face is formed on the inner peripheral side of a tip portion of the wall face of a flute which faces the rotational direction of a tool, an end cutting edge is formed at the tip of the main gash face, a sub-gash face is formed on the outer peripheral side of the main gash face so as to retreat via a stepped portion with respect to the main gash face, and a corner cutting edge which has a substantially convex arc shape from the tip of the sub-gash face to the outer periphery thereof is formed so as to be connected to the outer peripheral side of the end cutting edge.
Additionally, for example, Patent Citation 2 also suggests a radius end mill in which a gash is formed at the tip of a flute, an end cutting edge which is continuous via a cutting edge of a corner R from an outer peripheral cutting edge is formed at a tip-side side ridge portion of the wall face of the gash which faces the rotational direction of the end mill, the wall face of the gash which faces the rotational direction of the end mill is formed in a planar shape, and an intersection ridgeline of the wall face of the flute which faces the rotational direction of the end mill is made to intersect the cutting edge of the corner R.
In the radius end mills described in these Patent Citations 1 and 2, the main gash face and the sub-gash face are formed via the stepped portion, or the planar wall face of the gash which faces the rotational direction of the end mill is formed such that the intersection ridgeline with the wall face of the flute which faces the rotational direction of the end mill intersects the cutting edge of the corner R. Thereby, chips can be divided by the stepped portion or intersection ridgeline, and processability of chips can be improved.
[Patent Citation 1] Pamphlet of International Publication No. 2004/058438
[Patent Citation 2] Japanese Unexamined Patent Application Publication No. 2008-110472